The present invention relates to a method and apparatus for winding up a moving paper web to form a roll. The following references are relevant:
(1) DE 40 07 329 PA1 (2) DE 32 44 510 PA1 (3) FR 15 13 694 PA1 (4) GB 12 97 812 PA1 (5) US 19 23 670 PA1 (6) EP 0 483 092 A1 PA1 (7) U.S. Pat. No. 3,857,524 PA1 (8) DE 44 15 324
Winding machines for winding up paper webs can be arranged at the output end of a paper machine to roll the paper web arriving there into a roll (a so-called Pope-type reel). However, those machines are also used to rewind a finished paper roll so as to produce rolls of a very specific winding quality.
In all cases the paper roll should have very specific properties, in particular with regard to the winding hardness. The winding hardness should, in general, drop from a certain initial value to an end value. The drop should be as uniform as possible from the first inside layer to the last outside layer. It should have a certain gradient, i.e., it should not be too steep or too shallow. In no case should the profile of the winding hardness show abrupt changes, e.g. drop suddenly. No radial or tangential stresses, which could impair or destroy the paper web, should occur in the paper roll.
All of the foregoing have been objectives that were never accomplished. Winding machines of known construction instead produce, for instance, paper rolls in which the core is extremely soft or extremely hard and in which towards the end, at about 4/5 of the diameter of the roll, a strong drop in the winding hardness occurs. As a result, the first part, i.e., the extremely soft or hard core, is useless, since the web is compressed in this part and bursts so that this part must be thrown away as waste. In the end region in which the paper roll was not wound up with sufficient hardness, lateral displacement of the layers relative to each other occurs, so that the end sides of the finished roll appear frayed and the edges of the web can be easily damaged.
A poorly structured core with a hardness too great or too small does not permit a proper build-up of the rest of the paper roll. The problem is particularly serious in the case of pressure sensitive papers, for instance non-carbon papers, in which pressing of the reel spool with the developing paper roll present thereon against the shell of the carrier drum for the roll is subject to narrow limits.
In the method according to reference (1) DE 40 07 329 from page 1 herein, the developing paper roll is, as mentioned, displaced in a horizontal direction corresponding to the growth of the roll. The paper roll reaches an enormous weight which can exceed 100 tons. For this reason, the paper roll can, upon its growth, in any event not be pressed against the press drum in such a sensitive manner that variations in the line pressure can be avoided.
Reference (8) DE 44 15 324 from page 1 herein describes a winding machine for winding up of a paper web on a reel spool with a central drive. This machine comprises a winding station, a receiving station and a press roll without a drive. The press roll is continuously applied against the circumference of the secondary roll up to the winding station. The web is conducted in such a manner that it constantly enters the entrance nip without wrapping. The diameter of the press roll is as small as that of a standard web-guide roll. Due to insufficient flexural strength, it is therefore not suitable for the application of line pressures of any desired strength, in particular not for extremely large web widths, i.e., up to about 10 meters.
A special device in this case conveys a secondary reel spool and the press roll coupled with it up to the level of the winding station from which a previously wound paper roll was removed. The lift drive required for this produces an expensive construction.
This reference describes the following method: An empty reel spool is supported, together with a driveless press roll, on a vertical carriage. The reel spool and the press roll can be moved up and down on the carriage. Winding starts on the reel spool in a first upper position. The reel spool is then lowered onto horizontal rails together with the press roll and is moved into a fixed first position on the rails. During these steps, the winding process continues. In this first position, the paper web is wound up to form a complete roll, is brought into a delivery position and is then removed from the machine.
In the method according to reference (8) the reel spool is also initially wound in a first position, then lowered onto the rails where winding is then completed in a second position. Upon the lowering onto the rails, a jolt can occur which affects the circumferential force and again results in irregular winding hardness.
Another important disadvantage of this method is that the paper web is directly introduced into the press nip between the press roll and the reel spool, i.e., without, in this case, wrapping around the press roll. The inventors recognized that this leads to air inclusions between the individual layers of the developing paper roll.
U.S. Pat. No. 3,857,524 (reference 7) discloses a winding machine which operates in accordance with the Pope-type reel principle. A Pope-type reel in this case starts a first reel spool. As an alternative, a reel spool-starting device or "acceleration device" (column five, lines 61 to 67) is provided. The reel spool is swung around the circumference of the Pope-type reel and arrives on horizontal rails whereby it is pressed against the Pope-type reel. After cutting the moving web, the winding process on the reel spool commences. The Pope-type reel transmits a torque to the circumference of the reel spool and the developing paper roll. The winding up takes place, in this case, exclusively by application of force acting on the circumference. As soon as the paper reel is full, it is removed, driven by an "enveloper roll 31", from the Pope-type reel to create space for a following empty reel spool. The disadvantage of this machine is similar to that of the machine according to reference (1). In addition, there is no central drive for the reel spool. As a result, development of the winding hardness cannot be controlled as desired. Furthermore, the web tension between the Pope-type reel and the paper roll removed therefrom for cutting the web cannot be controlled as desired.
EP 0 483 092 A1 (reference 6) discloses the following method: An empty reel spool is accelerated to the speed of the web, is then placed on horizontal rails, is pressed against a "winding cylinder" and the leading end of the web is fed onto the empty reel spool. The paper web is then wound up until it forms a complete roll. The winding cylinder is in this case stationary, while the reel spool with the developing roll of paper is displaced on the rails to an extent corresponding to the growth of the paper roll. In this connection, a central drive and a circumferential drive act on the roll. Once the roll is completed, it is brought into a delivery position and is removed from the machine, while a new reel spool is accelerated and lowered onto the rails. Also in this case (as with references 1 and 7) it is not possible to set the line pressure between the winding cylinder and the developing paper roll to any desired values a sufficiently sensitive manner.